The development of relatively small-scale earth-working tools has been the subject of great thought and effort over the years in view of the widespread need for convenient, workable tools of that sort.
Moulton, U.S. Pat. No. 4,351,396, Sept. 28, 1982, is directed to the basic form and mechanics of a type of power hoe head which is known and which has been found to be attractive. That basic form incorporates into the head a motor, an axle which is parallel to the shaft of the motor, a pair of hoeing tines each extending first generally downwardly from the vicinity of the housing, then generally downwardly and inwardly, and then generally upwardly and inwardly. A motor shaft gear is opposite an end portion of the axle which end portion carries a gear for rotating the axle which meshes with the shaft gear. The two hoeing tines move 180.degree. out of phase with each other, in pendulum-like oscillation from two rotatable spindles. Chery, U.S. Pat. No. 3,935,905, Feb. 3, 1976, discloses a head which is comparable to the head in Moulton in some respects, but clearly distinct in other important respects. In Chery, the hoeing action is accomplished by a U-shaped cutting blade carrying front and back cutting edges therealong, which moves forward and backward.
Pfeiffer, U.S. Pat. No. 3,710,870, Jan. 16, 1973, incorporates prong-like tines configured in a generally horizontal plan and a gear-train arrangement from a motor in a similarly horizontal plan from the back of the tiller toward the front. The tiller is adapted for use on one's hands and knees. Brooks, U.S. Pat. No. 2,816,495, Dec. 17, 1957, incorporates a somewhat comparable gear-train in a mechanism which hoes using twirling prong-like implements. Ditlevsen, U.S. Pat. No. 1,827,074, Oct. 13, 1931, in a tool having a rather traditional hoeing implement, incorporates another gear arrangement employing gears at angles to one another.
Burke, Great Britain, Pat. No. 653,985, published May 30, 1951, incorporates legs, which move 180.degree. out of phase with one another carrying cutting blades. The apparatus is rather large and complex and is moved on wheels.
A number of other patents are exemplary of the variety of forms of implements for cultivating or otherwise interacting with the earth which have been attempted and of the search for such forms which are convenient and workable: Bolongaro, U.S. Pat. No. 2,550,522, Apr. 24, 1951, Richardson U.S. Pat. No. 3,548,953, Dec. 22, 1970, Kelsey, U.S. Pat. No. 2,779,259, Jan. 29, 1957, Foster et al., U.S. Pat. No. 4,003,436, Jan. 18, 1977, and Bills, U.S. Pat. No. 3,756,324, Sept. 4, 1973. Bolongaro and Bills, also with other of the initially referenced patents as noted, are exemplary of the types of forms of earth-working tools which have traditionally employed wheels.
Also, in a somewhat more general context, powered trench digging is typically accomplished by, for example, large, heavy duty apparatus incorporating a blade which rotates into the earth or apparatus incorporating a multi-sided digger to trap the soil therebetween. Similarly, powered sod cutting is typically carried out by, for example, large apparatus on wheels which incorporates a blade which reciprocates under a strip of sod to cut the strip.
The present invention, in a powered earth-working tool head, provides highly advantageous linkage between an earth-working member which undergoes a pendulum-like oscillation in accomplishing such working, and a prime mover which is distant from the immediate vicinity of the head. It also advantageously incorporates a wheel-roller arrangement in a head of that type. The invention, in a head incorporating the pendulum-like oscillation and the related mechanism to accomplish such oscillation, further provides particular specific, advantageous forms for trench-digging members and sod cutting and raising members.